+ We need a greater understanding of our cities’ green infrastructure as we design and deliver ever more populated urban environments.

Rapid urbanisation and migration continue to challenge the nature of our planet. In addition, pressures from climate change and flooding mean that cities need to find natural ways to adapt. I believe we need to understand and prioritise Green Infrastructure if we are to design sustainable, densely populated cities.

Green Infrastructure (GI) provides the ‘ingredients’ for solving urban and climatic challenges, by building with nature. GI is defined by the UK communities agency as a ‘network of multifunctional green space, urban and rural, which is capable of delivering a wide range of environmental and quality of life benefits for local communities’. GI is not just conventional open green space but encompasses parks, woodlands, street trees, allotments, private gardens, green roofs and green walls.

GI provides psychological, social and health advantages and a connection to nature, as well as a host of environmental benefits. Future cities will only prosper if they are understood as a complex adaptive system, where the relationship between humans and nature are entwined. However this complex relationship is often insufficiently considered during the design process, leading to negative environmental and social outcomes.

There are many connected GI and human elements to consider with any new built environment project. For example, we know that light regulates seasonal and daily cycles of many plants and animals, and that globally there is a 6% increase in artificial lighting per year. Scientists are now considering the possibility that the direction, brightness and wavelength of urban artificial lighting could lead to growth deformities in plants, with subsequent impacts to reliant animal species.

It has already been shown that climate change is disrupting flower pollination, causing bees to fly before flowers have bloomed and potentially affecting crop yields. It is clear that the dangers of unforeseen impacts on nature are real. Could a similar cycle of disruption resulting from other human influences affect the lifecycle of urban plants and animals?

Some cities are already grappling with these issues pragmatically. For example, two major rivers flow through Philadelphia, but in the last 100 years widespread urbanisation has concretised and restricted these rivers and sewers, increasing impervious surfaces and ultimately increasing stormwater flooding.

The city decided to use GI to restore the area’s natural capacity to capture water, using a multi-pronged strategy that included providing people with free rain barrels and replacing 30% of the city’s tarmac pavements and roads with porous ones. The Philadelphia Water Department also switched to a water metering system to monitor the volume of storm water that properties and businesses produce, subsequently incentivising them to retrofit their sites to include GI so that less water ends up in the sewer system.

However, implementing GI also brings many obstacles. Ownership, cost, maintenance, space and knowledge of the benefits prevent many local authorities from implementing GI. Furthermore, public safety and vandalism can prove to be challenging to overcome in some cases.

Designers and planners need to adopt a holistic way of thinking of these interdependent relationships when considering GI in city development. Additionally, relevant environmental impact data must be kept up to date. There also needs to be sufficient scientific understanding of the needs of various plant species to survive the ongoing impacts of a heavily human-modified landscape.

To improve the way GI is dealt with requires greater awareness of these issues, driven through continued research and public dialogue. Only then will our cities coexist successfully with Green Infrastructure.

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Steve Dalton

From a security/public safety perspective the greening of an urban environment can provide opportunities as well as challenges and can support initiatives such as Crime Prevention Through Environmental Design (CTED). Green walling, as an example, is an excellent counter to graffiti - in the right circumstances. We in the resilience and security sphere fully support the greater use natural solutions where circumstances allow and look forward to the day when there are greater opportunities to be creative with green solutions.

Marco Pluijm

Excellent article. To which i may add maybe another topic. And that's the element of climate change, in particular the fact that climate change induced extreme weather events are coming faster than originally anticipated for and with greater intensity. In terms of floodwater control, green infrastructure is absolute crucial and becomes therefore more and more important. With regard for cities along coasts and rivers, elements as protect and sea level rise add to the equation. One of the reasons why I have developed the Resilient by Nature approach. Base don what we can learn from those systems which seem to be resilient by themselves, and transfer that knowledge to other place which are not so well able to cope with these phenomena. For instance NYC would be a place which can benefit from this approach. You can find some more information about the "Resilient by Nature" onhttp://www.slideshare.net/MarcoPluijm/resilient-by-nature-marco-pluijm-28062016 . Happy to provide additional information. Kind regards, Marco Pluijm

John Moss

It would be hard to disagree with anything you say, and it's all very much to the point. But when it comes to "greater awareness of these issues" I have to be non pc and hammer away at the fact that in most urban analyses we are forced into dealing with symptoms, rather than with causes, of the diseases.

The real disease, lurking in the background is gross over population of our planet by humans, with no real attempts to limit population growth let alone to reduce our numbers to a sustainably green level. The reason it lurks behind blind eyes is partly political but the reason the politics works is our basic human instinct to reproduce. We don't accept that as with other instincts it has to be limited in the long term interest of humanity. Another aspect of the problem is the current view that the order of importance of matters that lead to human survival is safety, food, thermal comfort, a "home" and finally indulgence in children. Indulgence because as far as humanity is concerned there is no danger of our species dwindling away to nothing through lack of our reproduction. But the possible causes of an unwanted and very messy dwindling away are already apparent in scarcity of food, water, other resources and of simple "elbow room". Because of these pollution, civil unrest and even migration, the end symptoms, are in themselves becoming untreatable.

It's all much closer to home than we would like to think. How does the UK deal with the proposed(?), projected(?), increase of its population from the current overcrowded 65m to 85m by 2025 with the increasing competition for land for food, water, housing and industrial uses? This last because to be sustainable we have to export either people or goods.

Andrew Hoolachan

This is Malthusian thinking. Limits to population growth are arbitrary; we can sustain far more people with the right politics, technologies and design.

The idea that there is some ideal balanced state of human-environmental relations has no basis in scientific thought, but rather is a contested idealism. What should the ideal population of the world be and why? Who gets to make that decision? Which countries should slow their populations?

Land in the UK for example is used very inefficiently e.g. Greenbelts. Our cities could be denser without feeling crowded through could urban design e.g. Paris. We could use less land globally for farming e.g. vegetarianism.

John Moss

Malthusian, yes but he was never wrong about the long term with unrestrained growth, and we are plainly within sight or even reaching that point in the UK. It seems to me that the UK and many other places, from the Amazon rain forest to the Sahel and the Horn of Africa, have reached the point where the natural resources, and not just the possible food production, no longer support both the current population and the ecosphere together in a truly sustainable way. OK, what is needed could in the shortish term be supplied by other parts of the world or partially treated through huge migrations, and we can destroy most of the rest of the ecosphere, "unwanted" animals and plants alike to do it, but that doesn't mean that populations can continue to grow without check even with radically changed social and political attitudes to how we live.

It isn't simply a matter of politics, new technologies and more efficient usage. Food and water production is limited by climate and land areas, mineral resources by the accessible areas of the planet, and in the UK by increasingly deadly pollution through the up-and-coming need to manufacture what the rest of the world says it needs. There is no alternative to this last given the projected rate of population increase.

My plea is that Malthusian arguments should cease to be "non-pc" along with the doctrines of some of the power based political theorists and religious sects and the closely bound in economic theory that even a slowly contracting population is bad news.

veronique.jardy@arup.com

a) Stating that the greenbelts are inefficiently used and we could get denser cities is a curious way to see things.

So, we should build on most of the green spaces just because we can? You may not mind being surrounded by concrete, but not everybody feels the same.

You're talking about Paris. Well, I'm from there and believe me, it is not a nice place to live. Many suburban towns have no or tiny green spaces, they're overbuilt and overpopulated. I grew up in one of those towns - the quality of life is next to zero. And guess what, they are the ones with the highest level of crimes and aggressive behaviours.

Oh, and I won't even mention the level of pollution we get as soon as the temperatures reach 23 deg C.

b) If you use less land for farming, how do you expect to feed the constantly increasing populations?

If I understand well, your view is: let's build on as much the land as we can and let's ignore the problems that will inevitably arise from doing so. And as humans, we are superior to any other living creatures on earth, so we can multiply as we wish, and let's destroy nature and animals habitats so that we can take their place.

You seem to forget just one little fact: we need nature to live - It is necessary for our health and psychological equilibrium.

Refusing to accept the fact that human overpopulation will eventually cause serious problems (even higher level of pollution, shortage of living space, lower food resource, to name a few) is selfish (but I guess you're going to say that this is not scientifically proven).

But as John said, this is a non-pc subject. We're not talking about killing people, here!, but to be sensible and to have a limited number of children per family.This is a global issue and governments/countries should act now. Unfortunately, politicians will never touch that subject: too sensitive and too much trouble. I guess they prefer to leave their successors to face a situation that could be avoided if only we had the courage to deal with it while we still can.

I truly feel sorry for the generations to come, and do not envy them...

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